This invention pertains to ramps onto which the wheels of a vehicle such as an automobile, motor home, truck, bus, trailer or the like may be rolled to raise the wheel and a corresponding part of the vehicle so that access to the underside of the vehicle is more easily achieved.
In the earlier days of the automobile when the opening for draining oil from the crankcase of the engine became located at the bottom of the crankcase beneath the engine, access to that facility was almost exclusively from beneath the car. It therefore became quite common for service stations to build fixed ramps for the car to be driven onto. A pair of rails at a height of 3 to 4 feet above the ground was used, with a sloping pair of tracks following the car to be driven onto the upper tracks. Then a worker could crawl beneath the car as it was elevated and remove the drain plug to drain the used crankcase oil from the engine to be later replaced by fresh oil.
Later, oil pits into which the worker would climb down became common, to be followed by elevating hoists adapted to raise the car by hydraulic or pneumatic pressure. Each of these expedients worked successfully, but all were generally beyond the budget of the usual owner of the car.
Currently, large numbers of motorists choose to do some of their own maintenance including such expedients as changing oil, checking steering gear, hydraulic brake lines, shock absorbing struts and the like. However, most jacks, because of their relatively narrow base, are inherently dangerous for giving such access. Individual wheel ramps having a much broader base are comparatively much safer in that they rarely tip over to drop the vehicle. However, in order to be strong enough to carry the wheel and that wheel's portion of the vehicle weight, the ramp must be made of a relatively heavy structure. Thus the weight makes the ramp hard to move and therefore undesirably clumsy for ordinary use.
In order to avoid the difficulty of portability of a strong enough ramp having a relatively broad base for safety, the present invention uses retractable wheels on which the ramp can be moved, and which can be retracted into the base so that, when the ramp is used, the base rests firmly on the floor. The action is completely mechanical so that no special upkeep of the retraction mechanism is necessary. Further, the cost may be kept reasonable by the use of relatively simple mechanical means.